The manufactured articles, also in the form of plates, consisting of mixes of hydraulic binders such as cement, reinforced with open nets of fibrilled synthetic films, in particular polyolefinic films, are currently known in the art.
Said manufactured articles have high physical-mechanical characteristics, and more particularly they show high resistance to bending stresses, a high tensile strength, high impact resistance, a high fatigue strength, a high resistance to low temperatures and to water permeability and other properties that make those articles particularly suited for use in the building industry.
The continuous manufacturing process for such reinforced manufactured articles shows, however, a number of drawbacks that are mainly due to the fact that the incorporation into the hydraulic binder of one or more net-shaped structures of the previously mentioned type, each formed by a plurality of superimposed fibrilled polymeric films, hardly leads to a uniform, capillary diffusion of the binder into the net-shaped structure. In fact, especially when the manufacturing process is conducted at industrially competitive production rates, air bubbles form and portions of the reinforcing net are not uniformly impregnated.
Various processes and devices have been suggested for the preparation of such manufactured articles made with hydraulic binders and reinforced with either metal nets or with fibers or nets of natural, artificial or synthetic polymers. All the considered known devices and processes show, however, several drawbacks which unfavorably reflect on the quality of the produced reinforced plates, the characteristics of which turn out to be non-homogeneous and rather low grade, with a consequent prejudice to their practical application.
More particularly, in the known devices the feeding of the cement at the cement station does not occur uniformly as far as its quantity and distribution, with respect to the feeding of the reinforcing net, are concerned. Moreover, no account is taken of the air dragged along by the advancing net, while the contact between net and cement is, in general, carried out in such a way as not to ensure either the homogeneity of the composite or the correct impregnation of the net by the mix. Thus, the composite manufactured articles obtained are nonhomogeneous and have poor physical-mechanical characteristics. Moreover, no sizing, levelling and superficial finishing systems of the plates are foreseen so as to obtain commercially acceptable products.
Lastly, since the contact net/mix is only superficial, the air, trapped in the reinforcing structures, is not expelled, so that the adhesion between cement matrix and the reinforcing net is irregular and the structure of the composite article shows discontinuities, both on the surface and inside, due to the inclusion of air bubbles.